1. Field of the Invention
The invention relates to the field of testing and monitoring the integrity of lines, particularly twisted pair lines.
2. Prior Art
Twisted pair lines have been used for many years in telephony and countless buildings are wired, particularly in a star configuration, with twisted pair lines. It is a relatively expensive task to rewire structures to provide, for example, coaxial cable which is perhaps preferred for local area networks.
There are many commercially available systems which utilize twisted pair lines in local area networks such as in Ethernet networks. The general architecture of these systems is described in this application in order to set the environment in which the present invention is used.
There are existing techniques for monitoring and testing the integrity of twisted pair lines used in networks. IEEE 802.3 10 BASET describes a somewhat standard technique. Link test pulses are sent and received periodically to test the integrity of the line. These pulses are narrower than data so that they are not mistaken for data. One of the problems which occurs with this technique is that the pulses sometimes collide with data pulses thereby destroying the data pulses. Another problem is that in hub-to-hub connections, one hub must be a master (uplink/downlink) hub and so designated. As will be seen with the present invention, there is no master in a hub-to-hub connection.
As will be seen, the system of the present invention utilizes direct current voltages and currents for testing the lines, and thereby provides a less complicated, more reliable system.